Small arms design has moved past using fixed stock elements to using adjustable or modular components. Adjustable or modular components are used to configure a firearm for specific uses or missions. For example, U.S. Pat. No. 3,348,328 issued to Roy discloses an adjustable stock for use in conjunction with a CAR buffer tube. A buffer tube is a tube mounted to the back of a firearm receiver. In most applications, when the firearm is discharged, the bolt travels back and into the buffer tube while a spring, called the buffer spring, supplies a force for decelerating the bolt and returning it to a forward position. FIG. 1B of U.S. Pat. No. 5,941,005 illustrates a spring in a buffer tube.
Roy, however, uses a specially formed CAR buffer tube for use with his adjustable stock. Many buffer tubes are simply cylinders that are appropriately sized for holding a buffer spring and decelerating the bolt. The CAR buffer tube is a buffer tube with an elongated rib and a groove. The CAR buffer tube is a standard part of certain military issue small arms. U.S. Pat. No. 3,348,328 contains illustrations of a CAR buffer tube, a stock element that slides onto the CAR buffer tube, and a locking mechanism that can lock the sliding stock in a variety of positions.
Standard CAR buffer tubes, such as those used with the M4 and M16 carbines, have been attached to shotgun receivers. Some shotguns equipped with CAR buffer tubes do not use a buffer spring within the CAR buffer tube to achieve semiautomatic operation.
FIG. 11, labeled as “prior art”, illustrates a side view of an idealized CAR buffer tube. A cylindrical tube 1101 has a threaded end 1102 for attachment to a receiver and an elongated rib 1103 extending radially.
FIG. 12, labeled as “prior art”, illustrates a bottom view of an idealized CAR buffer tube. The groove 1201 in the elongated rib 1103 can be seen. Holes 1202 are positioned in the undercut groove 1201. An adjustable stock can be locked into position by a pin pressing into a hole 1202.
FIG. 13, labeled as “prior art”, illustrates a cut view of an idealized CAR buffer tube. The cylindrical tube 1101 has a sidewall 1302 and an opening 1301 that can contain a buffer spring. The groove 1201 in the elongated rib 1103 can be seen.
Other inventors have refined Roy's adjustable length butt stock. For example, U.S. Pat. No. 6,874,267, U.S. Pat. No. 6,651,371, disclose modular gunstock systems. Like Roy, these two inventions use a specially designed replacement buffer tube. An armorer trained to work on small arms replaces the original buffer tube with the replacement buffer tube. Users who are less specialized than the armorer can then configure the remainder of the modular gunstock system. Another example is U.S. Pat. No. 6,925,744 that refines Roy's adjustable length butt stock by adding compartment modules to the moveable butt stock element.
FIG. 14, labeled as “prior art”, illustrates a stylized toy replica 1401 firing a pellet 1402. Many toy replicas, such as Airsoft toys, are pellet firing small arms replicas. Hobbyists enjoy engaging in mock non-lethal battles using toy replicas because they are realistic looking and fire non lethal, although often painful, pellets. Realistic toys are also used in small arms training because the toys can have the same weight, size, and accessories as firearms used in combat or police work. The toy replicas are often realistic enough that many after market accessories can be used with both small arms and with toy replicas. A toy replica of an AR16 or M4 carbine, however, uses an imitation CAR buffer tube 1403 and not a real CAR buffer tube. As such, a small arms accessory requiring replacement of the buffer tube is not suitable for use with a toy replica. The illustration of FIG. 14 is stylized because, from a distance, a toy replica can be indistinguishable from an actual small arm. Those practiced in combat training and police training are familiar with toy replicas.
FIG. 17, labeled as “prior art”, illustrates a firearm 1701. More specifically, the firearm is an M16 rifle or its' civilian counterpart the AR15. The M16 1701 buffer tube is a cylindrical buffer tube inside the stock 1702. The buffer tube is threaded to the lower receiver 1703 on one end and has a threaded hole in the other end. A bolt threaded into the threaded hole bolts the stock 1702 to the buffer tube.
FIG. 18, labeled as “prior art”, illustrates a firearm 1801 with an exposed buffer tube 1802. The firearm is an M16 rifle as in FIG. 17. The butt stock is removed so that the buffer tube 1802 can be seen. A bolt 1803 such as that for bolting on the stock, is threaded into the threaded hole at the end of the buffer tube 1802.
Prior art systems, however, require trained armorers or lack a comfortable cheek weld for a marksman. As such, systems and methods are needed to address shortcomings in the prior art.